Infectious diseases are caused by various pathogens: virus, bacteria, fungus, spores, etc. Once on or within the body they replicate and ultimately can cause infection and illness, sometimes resulting in death. Pathogens reach the body through contaminated food, aerosolized pathogens in air or on dust, human contact with surfaces or human-to-human contact. Hands are a significant vehicle for disease transmission. Thus, hand washing is one important means of preventing the spread of infection and germs that can cause colds and flu.
In a hospital or other health care environment health care workers and physicians are significant factors in disease transmission from patient to patient by virtue of inadequate attention to, or inadequate technology for, hand sanitation. Sanitation is defined as a reduction of pathogens of any given type by a factor of 104. The traditional method of sanitizing hands is hand washing with soap or anti microbial soap and drying with sterilized towels. Recently, the application of alcohol formulations followed by a short drying period has become a common hand sanitizing process. Hand washing, possibly including the forearms, is capable of removing a fraction of the transient pathogens, and alcohol rubs kill many but not all types of pathogens. However, each technique has inadequacies in that elimination or reduction by a factor of 104 of active pathogens is not always complete or assured, does not cover 100% of the area to be sanitized and not always possible for multiple reasons. The result is variable; there is no certainty in any particular instance.
Extended application time improves the protection. For example, surgeons scrub for many minutes to improve the removal of pathogens, and nurses and other healthcare workers wash their hands frequently, and as a result, cause their hands to become painfully sore thereby making it difficult to use the technique consistently. Thus, as the required application time increases and the unpleasant side effects increase, compliance with sanitization procedures decreases, Surgeons may not scrub for the necessary length of time—approximately 10 minutes—or with the necessary vigor, and nurses may avoid hand washing to reduce the discomfort associated with the hand irritation that can be exacerbated by wearing latex gloves. Moreover wearing latex gloves does not solve these problems. As health care professionals go from patient to patient, they can transport pathogens on the surfaces of the gloves just as they can on bare hands. Furthermore, one touch of any surface by the hand contaminates the hand. All the effort at sanitation can be lost by a single touch by the hand of a surface or by settling of aerosols containing pathogens or dry pathogens drifting in the air. The contaminated hand is a major vehicle for transmission of pathogens to the patient and possibly the primary source of hospital acquired infection spread. Furthermore, the gloves cannot be easily washed while being worm, the gloves are not replaced as often as should be to limit the transmission of disease and constant replacement of gloves increases costs associated with patient care. It is generally understood that the purpose of the gloves is to protect the healthcare worker from the patient, not the patient from the healthcare worker.
The necessary time for effective use of alcohol including drying is tens of seconds. One factor that is cited as a significant inconvenience is the time required to achieve substantial reduction of the number of pathogens (e.g., 99.99%), or missed areas and thus the process of sanitation is frequently bypassed. Alcohol rubs are ineffective on spores. Another factor is that the use of alcohol dries the epidermis, which is supposed to function to protect the moisture of the skin. Hence the skin sometimes can become irritated and the procedure is bypassed.
Bare hands are also a major element in the spread of infection in schools. The cost to schools of absence is very high. Students can miss class time and carry illnesses home. Hence, proper hand sanitation in the school environment is also financially important to the schools, to the students and to the parents. Washing hands is typically not practiced as frequently as desired or in a sufficient manner. Moreover, in many developing countries, the sanitary and hygienic conditions at schools are often very poor, and can be characterized by the absence of properly functioning or existing water supply for sanitation or hand washing facilities. Studies have demonstrated that the absentee rate is reduced by 50% with proper hand washing.
Clean hands in restaurant settings are similarly critical to prevent the spread of disease. The FDA reports that poor personal hygiene in a food service environment is a critical area that needs immediate attention and makes the following points with respect to personal hygiene: proper, adequate hand-washing, prevention of hand contamination, good hygienic practices, hand-washing facility, convenient/accessible, and hand-washing facility, cleanser/drying device.
A summary of several studies and initiatives concerning hand-hygiene can be found in an article by Kelly M. Pyrek, entitled “Hand Hygiene: New Initiatives on the Domestic and Global Fronts,” published on Jun. 1, 2006, and available at a web site maintained by Infection Control Today (ICT), the entire disclosure of which is hereby incorporated by reference.
Ultra-violet germicidal irradiation (UVGI) can be use to deactivate pathogens such as anthrax, smallpox, viral hemorrhagic fevers, pneumonic plague, glanders, tularemia and drug resistant tuberculosis. Pathogens that have a relatively thick cell wall, such as spores, are more resistant to UVGI because the cell wall is not easily penetrated. However, with greater intensity and longer exposure times, even the more resistant pathogens are deactivated by UVGI.
The effectiveness of UVGI derives from a band of UV-C radiation centered at a wavelength of 265 nm plus or minus 30 nm. The UV-C radiation modifies the DNA and eliminates the ability of a pathogen to reproduce. Pathogens that can't reproduce are not infectious, and are therefore harmless. Germicidal reduction of the density of reproducing pathogens in air is based on the ability of UV-C radiation, from an emitted spectral line of mercury excited by a low pressure gas discharge, typically in argon, centered at λ253.7 nm, to eliminate the ability to reproduce of a percentage of pathogens of a given type in the air surrounding the tube. Other types of tubes are capable of producing radiation in the UVGI band, for example xenon discharge tubes (see e.g., http://xingguang.en.alibaba.com/group/200028075/Xenon_lamp.html). The percentage depends on the product of UV-C intensity at the pathogen and exposure time, typically called the dose.
Radiation intensity is a measure of radiant power incident per unit area. If a pathogen is in the presence of germicidal radiation of a given wavelength for a given exposure time, the integral of the radiation intensity experienced by the pathogen over time determines the radiant exposure per unit area or dose. The surface area of the pathogen defines the actual energy incident on the pathogen. Some of the incident energy is absorbed, which results in the deactivation of the pathogen. Deactivation is also referred to as inactivation.
A study by P. W. Brickner et al. discusses the duration and intensity of exposure to radiation having a wavelength of 253.7 nm that is required to deactivate various pathogens. See P. W. Brickner, R. L. Vincent, M. First, E. A. Nardell, M. Murray, and W. Kaufman, “The Application of Ultraviolet Germicidal Radiation to Control Transmission of Airborne Diseases: Bioterrorism Countermeasure,” PUBLIC HEALTH REPORTS, Vol. 118, pp. 990-114, March-April 2003 (available at http://www.publichealthreports.org/userfiles/118—2/118099.pdf) (hereinafter, “the Brickner study”).
The following table includes a sample of the data presented in the Brickner study. The table describes the average flux used in the experiment not the actual absorbed energy. Differences reflect both different size of the pathogen and different required dose.
Examples of actinic exposure data for 90% reductionin colony formationRequired Radiant Exposure forMicroorganism90% Deactivation (J/m2)TypeStreptococcus (various)18.4 to 61.5BacteriaTubercle bacillus100.0BacteriaBacillus anthracis45.2BacteriaSalmonella tiphi21.4BacteriaDysentery bacilli22BacteriaMicrococcus luteus197BacteriaDeactivation to 99% requires twice the radiant exposure for 90% deactivation. Sanitation or 99.99% deactivation requires four times the radiant exposure. Hence for Tubercle bacillus sanitation requires a radiant exposure of 400 J/m2. If the intensity at a surface is 500 watts/m2 the time required for sanitation of the surface for the particular bacteria is 0.8 seconds.
UVGI has not been employed as an alternative to soap or alcohol based hand sterilization since it cannot be used on bare skin. What is needed in the art is a system and method for effectively sterilizing hands using UVGI that avoids the negative side effects of traditional hand sanitation and more particularly a method and system for sterilizing gloved hands.